Like gyms or bars, lekking grounds are social performance spaces, where males spread their tail-feathers, inflate their impressive chests, and strut about, calling amorously to the lady birds. Ecologist Gail Patricelli of UC Davis captured this video of a lek near Hudson, Wyoming. US Fish and Wildlife Service named the grouse’s habitat, the Great Plains sage-steppe, one of the most imperiled ecosystems in America.

Photo by Phillip ‘Scooter’ Trosclair. Birds are often touted as the monogamists of the animal kingdom, with most bird species mating with the same individual and displaying biparental care, sometimes for many years. Their cousins, the reptiles, are no match for their faithfulness: most reptiles show no mate fidelity, let alone parental care. But a new study in the journal Molecular Ecology has shown that some alligators actually do...